Travel between Halloweentown and the ordinary, historical world (which Halloweentown residents call "The Mortal World") is only possible with magical aid, and only at regulated times (on Halloween), until the portal seals at midnight. In the second film they permanently open the portal between the mortal world and Halloweentown, and events of the third film breach the gap even more.

It is stated that many of the traditions of Halloween in the Mortal World are parallels based on regular traditions in Halloweentown. An example of this is how mortals wear costumes that mimic the creatures of Halloweentown, and are often depicted as being more frightening than they are naturally. In Halloweentown, the residents dress up every day, and most are much friendlier than humans generally depict them.

Although magic is present in many of the details of daily life of Halloweentown, it appears that only a limited number of persons actually practice or control magic. These people are mainly human, and are called witches (female) and warlocks (male). These beings appear human, but possess some sort of biological extra-sensory ability which allows them to harness magic unlike their "mortal" counterparts. Magic is also hereditary in their families.

The Halloweentown movies concern episodes in the lives of the Cromwell-Piper family. The family matriarch, Agatha Cromwell, has been a pillar of Halloweentown society for centuries. Her daughter, Gwen Piper, married a mortal and chose to leave Halloweentown for a life in the Mortal World. At the time of the movies, she is apparently widowed. She has decided to raise her three children (Marnie, Dylan, and Sophie) apart from magic, and thus rejects contact with Halloweentown and the influence of her mother.